OS/2 builds created from the THUNDERBIRD_3_0a3_RELEASE tags in the repositories
involved. Changes from the official mozilla-central sources were necessary to
fix a build break that was just present at the time of branching (patch 1) and
to be able to compile with the OS/2 compiler (GCC 3.3.5, patches 2 and 3). The
three patches are appended below.
The .mozconfig used is included here. Media support support is not yet activated
on OS/2, so HTML5 <audio> and <video> elements do not work in Shredder alpha 3.

Requires kLibc 0.6.3 to run.

Peter Weilbacher <mozilla@Weilbacher.org>, 2008-10-15

---------------------------------- .mozconfig ----------------------------------
mk_add_options MOZ_BUILD_DATE=20081015100000
mk_add_options MOZ_OBJDIR=x:/TB30a3/20081015100000
ac_add_options --enable-application=mail

ac_add_options --disable-debug
ac_add_options --enable-optimize
ac_add_options --disable-shared
ac_add_options --enable-static
ac_add_options --disable-tests

ac_add_options --disable-ogg

=================================== patch 1 ===================================
Bug 451278: work around GCC 3.3 bug that breaks building on OS/2

diff --git a/xpcom/string/public/nsTString.h b/xpcom/string/public/nsTString.h
--- a/xpcom/string/public/nsTString.h
+++ b/xpcom/string/public/nsTString.h
@@ -444,9 +444,14 @@
          *        the length of the string already contained in the buffer
          */
 
+#ifdef XP_OS2 /* Workaround for GCC 3.3.x bug. */
+      nsTFixedString_CharT( char_type* data, size_type storageSize ) NS_COM;
+      nsTFixedString_CharT( char_type* data, size_type storageSize, size_type length ) NS_COM;
+#else
       NS_COM nsTFixedString_CharT( char_type* data, size_type storageSize );
 
       NS_COM nsTFixedString_CharT( char_type* data, size_type storageSize, size_type length );
+#endif
 
         // |operator=| does not inherit, so we must define our own
       self_type& operator=( char_type c )                                                       { Assign(c);        return *this; }
diff --git a/xpcom/string/public/nsTSubstring.h b/xpcom/string/public/nsTSubstring.h
--- a/xpcom/string/public/nsTSubstring.h
+++ b/xpcom/string/public/nsTSubstring.h
@@ -496,7 +496,11 @@
          * this is public to support automatic conversion of tuple to string
          * base type, which helps avoid converting to nsTAString.
          */
+#ifdef XP_OS2 /* Workaround for GCC 3.3.x bug. */
+      nsTSubstring_CharT(const substring_tuple_type& tuple) NS_COM;
+#else
       NS_COM nsTSubstring_CharT(const substring_tuple_type& tuple);
+#endif
 
         /**
          * allows for direct initialization of a nsTSubstring object. 
@@ -522,7 +526,11 @@
       PRUint32    mFlags;
 
         // default initialization 
+#ifdef XP_OS2 /* Workaround for GCC 3.3.x bug. */
+      nsTSubstring_CharT() NS_COM;
+#else
       NS_COM nsTSubstring_CharT();
+#endif
 
         // version of constructor that leaves mData and mLength uninitialized
       explicit
@@ -530,7 +538,11 @@
 
         // copy-constructor, constructs as dependent on given object
         // (NOTE: this is for internal use only)
+#ifdef XP_OS2 /* Workaround for GCC 3.3.x bug. */
+      nsTSubstring_CharT( const self_type& str ) NS_COM;
+#else
       NS_COM nsTSubstring_CharT( const self_type& str );
+#endif
 
         /**
          * this function releases mData and does not change the value of
=================================== patch 2 ===================================
[OS/2] Bug 453705: workaround to fix builds break when compiling dom_quickstubs.cpp

diff --git a/js/src/xpconnect/src/qsgen.py b/js/src/xpconnect/src/qsgen.py
--- a/js/src/xpconnect/src/qsgen.py
+++ b/js/src/xpconnect/src/qsgen.py
@@ -457,6 +457,11 @@
                 "    nsCOMPtr<nsIVariant> ${name}(already_AddRefed<nsIVariant>("
                 "XPCVariant::newVariant(ccx, ${argVal})));\n"
                 "    if (!${name}) ${failBlock}\n")
+            if os.name == 'os2': # Workaround for GCC 3.3.x bug.
+                template = (
+                    "    nsCOMPtr<nsIVariant> ${name}("
+                    "XPCVariant::newVariant(ccx, ${argVal}));\n"
+                    "    if (!${name}) ${failBlock}\n")
             f.write(substitute(template, params))
             return
         elif type.name == 'nsIAtom':
=================================== patch 3 ===================================
Bug 458113: OS/2 build breaks after Implementation of user font set object

diff --git a/gfx/thebes/public/gfxOS2Platform.h b/gfx/thebes/public/gfxOS2Platform.h
--- a/gfx/thebes/public/gfxOS2Platform.h
+++ b/gfx/thebes/public/gfxOS2Platform.h
@@ -66,17 +66,17 @@ public:
                          nsStringArray& aListOfFonts);
     nsresult UpdateFontList();
     nsresult ResolveFontName(const nsAString& aFontName,
                              FontResolverCallback aCallback,
                              void *aClosure, PRBool& aAborted);
     nsresult GetStandardFamilyName(const nsAString& aFontName, nsAString& aFamilyName);
 
     gfxFontGroup *CreateFontGroup(const nsAString &aFamilies,
-                                  const gfxFontStyle *aStyle
+                                  const gfxFontStyle *aStyle,
                                   gfxUserFontSet *aUserFontSet);
 
     // Given a string and a font we already have, find the font that
     // supports the most code points and most closely resembles aFont.
     // This simple version involves looking at the fonts on the machine to see
     // which code points they support.
     already_AddRefed<gfxOS2Font> FindFontForChar(PRUint32 aCh, gfxOS2Font *aFont);